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Description:
Adult grizzly bears have a concave face, high-humped shoulders, and curved claws. Males range from 300 to 600 pounds, and females typically weigh 200 to 400 pounds. While some grizzlies have fur that looks frosted (hence, "grizzly"), their thick fur varies in color from light brown to nearly black. Distinguishing a grizzly from a black bear can be very difficult despite the grizzly's larger size, and shorter, rounder ears.
Life History:
As an omnivore, the grizzly bear eats both plants and animals. Approximately 80 to 90 percent of its diet is green vegetation, nuts, seeds, berries, and roots. Grizzlies also eat insects, and they often leave behind overturned stones and rotted logs. Most of the meat in the diet comes from animal carcasses, though the grizzly will occasionally prey on elk. In Alaska and Canada, salmon is an important food source. In the Greater Yellowstone and Northern Rockies regions, grizzlies will feed predominantly on whitebark pine seeds if given a large enough source.
Distribution:
In the early 1800s, an estimated 50,000 grizzly bears roamed across the western United States from the Great Plains to the Pacific coast. Today, their populations in the lower 48 states are limited to the Northern Cascades (Washington), Northern Rockies, and Greater Yellowstone Ecosystems.
Status:
Under the Endangered Species Act, the U.S. Fish and Wildlife Service listed the grizzly bear as threatened in the lower 48 states in 1975. Recovery efforts have been modestly successful in some regions. In November 2005, the U.S. Fish and Wildlife Service announced its intent to establish the Greater Yellowstone grizzly bear population as a "distinct population segment (DPS)" and to remove this DPS from the List of Threatened and Endangered Wildlife.
News:
In March 2007, the U.S. Fish and Wildlife Service announced that it is removing the Greater Yellowstone grizzly bear population from its status as "threatened' on the U.S. list of threatened and endangered species. Four other grizzly populations in the lower 48 states have not yet recovered and will continue to be protected as threatened species under the Act.
The Interagency Grizzly Bear Study Team (IGBST) is a cooperative effort of the USGS - Biological Resources Division, National Park Service, Forest Service, and the States of Idaho, Montana, and Wyoming. The IGBST conducts research that provides information needed by various agencies for immediate and long-term management of grizzly bears (Ursus arctos horribilis) inhabiting the Greater Yellowstone Ecosystem. IGBST annual reports and publications facilitate transfer of research results to the general population. These reports and publications are available on the IGBST website.
The Grizzly and Whitebark Pine
Grizzly Bear (Ursus arctos horibilis) [Photo: Jim Peaco, National Park Service]
The grizzly bear is an omnivore, eating both plants and animals. Approximately 80 to 90 percent of its diet is green vegetation, nuts, seeds, berries, and roots. In parts of their range, such as the Greater Yellowstone Ecosystem, grizzly bears depend so heavily on whitebark pine seeds that their survival has been linked to the presence of whitebark pine (Mattson and Reinhart 1997).
However, grizzly bears do not collect the seeds themselves; bears depend on red squirrels who collect the seed cones and store them in middens, which are piles of cones and debris that have accumulated over years of use (Koteen 2002; Mattson and Jonkel 1990; Mattson and Reinhart 1994). Grizzly bears will take cones from these middens, usually following squirrels to locate them (Mattson, Kendall and Reinhart 2001).
Whitebark pine seeds are large and more than 50% fat, providing a high-energy food source (Lanner and Gilbert 1994). In a good cone crop year, grizzlies will spend the fall feeding almost exclusively on whitebark pine seeds (Tomback, Arno and Keane 2001). Because female grizzlies rely on sufficient fat stores to get through both winter and reproduction (Mattson, Kendall and Reinhart 2001), female grizzly bears eat approximately twice the amount of whitebark pine seeds as male grizzlies (Mattson 2000).
Sources:
Koteen, L. (2002). Climate Change, Whitebark Pine, and Grizzly Bears in the Greater Yellowstone Ecosystem. Wildlife Responses to Climate Change: North American Case Studies. S. S. a. R. TL. Washington, Island Press: 343-414.
Lanner, R.M. and B.K. Gilbert (1994). Nutritive value of whitebark pine seeds and the question of their variable dormancy. In: Schmidt, W. and Holtmeier, F.-K., compilers. Proceedings - International workshop on subalpine stone pines and their environment: The status of our knowledge. USDA Forest Service, Intermountain Research Station, Ogden, Utah: 206-211.
Mattson, D.J. (2000). Causes and consequences of dietary differences among Yellowstone grizzly bears. Ph.D. Dissertation. University of Idaho, Moscow.
Mattson, D.J. and C. Jonkel (1990). Stone pines and bears. In: Schmidt, W. and McDonald, K., eds., Symposium on Whitebark Pine Ecosystems: Ecology and Management of a High Mountain Resource. Ogden, UT: USDA Forest Service, Intermountain Research Station: 223-236.
Mattson, D.J. and D.P. Reinhart (1994). Bear use of whitebark pine seeds in North America. In: Schmidt, W. and Holtmeier, F.-K., compilers. Proceedings - International workshop on subalpine stone pines and their environment: the status of our knowledge. USDA Forest Service, Intermountain Research Station, Ogden, Utah: 212-220.
Mattson, D.J. and D.P. Reinhart (1997). Excavation of red squirrel middens by grizzly bears in the whitebark pine zone. Journal of Applied Ecology 34:926-940.
Mattson, D.J., K.C. Kendall and D.P. Reinhart (2001). Whitebark Pine, Grizzly Bears, and Red Squirrels. Whitebark Pine Communities: Ecology and Restoration. T. DF., A. SF. a. K. RE. Washington, Island Press: 121-136.
Tomback, D.F., Stephen F. Arno and Robert E. Keane (2001). The Compelling Case for Management Intervention. Whitebark Pine Communities: Ecology and Restoration. T. DF., A. SF. a. K. RE. Washington, Island Press: 3-25.
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